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In this work, the early hydration reaction and mechanical evolution characteristics of graded fine tailing cemented backfill are studied. The hydration exothermicity and electrical resistance characteristics of backfill slurry with different lime sand ratios are tested, and the microscopic morphology characteristics of early hydration products are analyzed according to scanning electron microscopy (SEM). Finally, on the basis of uniaxial compression mechanical test results, the early hydration reaction process and the effect of the products on the strength evolution of the backfill are analyzed. The results showed that the exothermic process of slurry hydration underwent rapid reaction stage I, induction stage II, acceleration stage III, deceleration stage IV, and stabilization stage V. The volume resistivity underwent increasing stage I, decreasing stage II, and accelerated increasing stages III. The slurry lime sand ratio affects the hydration heat release and volume resistivity. The larger ratio is, the greater the hydration heat release rate and heat release, the more hydration products are generated, and the greater the volume resistivity. An increase in the lime sand ratio prolongs the induction time of the hydration reaction and increases the rate of the hydration reaction during the induction period. At the same time, it retards the growth of volume resistivity. The larger the lime sand ratio is, the stronger the retarding effect and the larger the retarding effect on the growth of slurry volume resistivity. The rate of the hydration reaction directly determines the formation speed of the backfill strength. When the main components of the filling material, C3S and C3A, are dissolved rapidly in water, much heat is released. The generated Ca(OH)2 reduces the volume resistivity of the slurry and accelerates the growth of the backfill strength; the AFt generated subsequently compacts the pores between particles, blocks the dissolution of ions, decreases the rate of heat release, and prevents the growth of backfill strength. The backfill strength increases rapidly from 0–3 d and slowly from 3–7 d. When the hydration reaction is basically completed after 14 d, the filling material is solidified overall, and its strength is basically stable. The change in backfill strength first increases and then gradually decreases until stabilizing. These research conclusions provide theoretical support and scientific guidance for mining to adopt graded fine tailings to fill the underground goaf and control the temperature of the deep stope.

In order to study the water-inrush disaster law of collapse column under the influence of interstitial material activation, a return air roadway of Shenhua Group was taken as the research object. The strength reduction and permeability mutation caused by rock destruction inside and outside collapse column and activation and loss of fillings were considered. FLAC3D simulation was used to study the characteristics of displacement, permeability coefficient, pore water pressure and water inflow of collapse column and surrounding rock in the process of roadway excavation. On this basis, the influence of fillings packed height of collapse column on water inrush was analyzed. The results show that: with the increase of the distance between roadway and collapse column fillings layer, the width and depth of the activated loss of collapse column fillings in the roadway floor will be larger and larger, resulting in the rock displacement between collapse column water-conducting layer and roadway bottom is increasing and the overall slip trend appears. Finally, when the roadway driving face exceeds 1 m of the collapse column central axis, the high-pressure water of the collapse column injects water into the roadway through the activation and loss channel of fillings. And the water inrush has the characteristics of large volume, suddenness and hysteresis. The larger the fillings packed height of collapse column is, the later the water inrush time node of collapse column relative to roadway excavation surface is. However, when the fillings packed height of collapse column reaches 22 m, water inrush will not occur in the collapse column.

In order to study the evolution process of interstitial material in Chang 8 reservoir, Through casting thin section, scanning electron microscopy, cathodoluminescence, carbon and oxygen isotope, laser Raman, electron probe and other analytical techniques, in-situ micro-zone temperature measurement analysis was carried out.The formation temperatures of chlorite, illite and carbonate cement in Chang 8 reservoir in Longdong area were determined by micro-zone in situ temperature measurement analysis,and the diagenetic sequence of Chang 8 reservoir interstitials was quantitatively analyzed. The study shows that the Chang 8 reservoir mainly develops five types of interstitial material, namely chlorite, illite, kaolinite, siliceous and carbonate cement, and the content of interstitial material is significantly different. The filling sequence of interstitial material in Chang 8 reservoir in Longdong area is : stage I chlorite rim→stage I carbonate cementation→stage I authigenic quartz→kaolinite+stage II authigenic quartz→stage I illite→stage II chlorite+stage II illite+stage II carbonate→stage III authigenic quartz→stage III illite→stage III carbonate→stage III chlorite. [ABSTRACT FROM AUTHOR]

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Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)